According to Their Deeds — Paul Robertson

Charles Beale lives happily in the shadows of Washington, D.C., as a respectable rare-books dealer. Or mostly respectable. He has a streak of the gambler in him and when a devoted client dies--a man deeply connected to the Justice Department--Beale eagerly regains the man's book collection...and soon finds himself with more than he bid on. In one volume, Beale discovers documents incriminating a host of major political figures--blackmail material that might have led to murder. Weighing questions of justice and mercy--and with a bull's-eye on his back--Beale must untangle a complicated knot of deadly lies and dangerous secrets.